The present invention relates to a rock drill.
The object of the present invention is to develop a rock drill with which the secondary cutting element(s) has/have a longer service life.
This object is attained, based on the features of the preamble of claim 1, by the characterizing features of claim 1. Advantageous refinements are described in the subclaims.
The inventive rock drill has a longitudinal drill axis, which intersects the first plane at a first intersection point and intersects the second and/or third planes at a second and/or third intersection point. The longitudinal drill axis and the first plane form a first acute angle in the direction of advancement of the rock drill, and the longitudinal drill axis and the second plane and/or the third plane form a second and/or third acute angle in the direction of advancement of the rock drill. Due to this orientation of the secondary cutting element in the direction toward the resultant force that acts on the secondary cutting element during the drilling operation—the resultant force being essentially composed of an axial component produced by the hammer pulse of the rock drill, and a tangential component produced by the rotation of the rock drill—the service life of the secondary cutting element may be increased considerably without changing any of the dimensions by directing the aforementioned, resultant force toward the center of mass of the secondary cutting element. The core of the present invention is therefore a spacial orientation of the secondary cutting element toward the force that acts on the secondary cutting element during hammer drill operation. Increased service life is attained by tilting the cutting element away from the direction of advancement, the cutting element being tilted via a slanted embedding in the front and/or rear lateral face such that the center of mass of the cutting element lies on a force vector that passes through the cutting edge.
According to the present invention, the first plane is oriented at an angle (α1) of approximately 10° to 25° relative to the longitudinal drill axis. As a result, an optimal orientation of the secondary cutting element in all conventional load situations is made possible.
The present invention also provides that the second plane and/or the third plane and/is oriented at an angle (α2, α3) of approximately 5° to 20° relative to the longitudinal drill axis. This makes it possible to roughly orient the secondary cutting element in an optimal manner.
According to the present invention, the angle (α1) between the first plane and the longitudinal drill axis is greater than the angle (α2, α3) between the second plane and/or the third plane and the longitudinal drill axis. This angular difference prevents the secondary cutting element from falling out of the groove in which it is retained, since every impact that the secondary cutting element experiences during operation causes the secondary cutting element to tilt in the groove in a braking or blocking manner.
The present invention also provides for a positioning of the secondary cutting element, with which the first intersection point is located in front of the center of mass, as viewed in the direction of advancement of the rock drill, and with which, in particular, the first intersection point is located between a drill bit tip and the center of mass. A compact design of the drill bit head is therefore ensured.
In addition, according to the present invention, a removal channel for drill cuttings is located in front of the cutting edge of the secondary cutting element, in the direction of rotation of the rock drill, the removal channel extending away from an end face of the drill head and into the conveying helix. It is therefore ensured that drill cuttings are carried away efficiently in front of the effectively operating, secondary cutting element.
The present invention also provides that the secondary cutting element is embedded in a groove formed in the drill head. This makes it possible to attach the secondary cutting element easily and effectively.
According to the present invention, lateral flanks of the groove define a fourth and a fifth plane, which have a fourth and a fifth intersection point with the longitudinal drill axis. This slanted orientation of the groove makes it possible to orient and/or position known cutting elements in a manner according to the present invention.
In addition, according to the present invention, the secondary cutting elements are located with mirror symmetry relative to the longitudinal drill axis. This ensures that the load placed on the rock drill is largely symmetrical.
Finally, the present invention provides that the secondary cutting element is designed as a component of a solid hard-metal head.
Further details of the present invention are described in the drawing with reference to schematically depicted exemplary embodiments.